MEDRADSC 3H03 Lecture Notes - Lecture 5: Light Field, Collimator, Stereoscopy
3 Feb 2020
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What do these items have in common: small pieces of lead to slide in collimator, not used much anymore, fared cone, dental imaging, cone, collimator, used to restrict beam to useful area. Functions of the collimator: shape the beam, gives us light/mirror system replicating radiation field exactly. Light field x-ray field alignment: 9 nickel test for light field radiation field congruence, we are allowed to be off by 2%, sid at 100, diameter of nickel is 2cm (100x2%=2cm) If its off by the width of the nickel it fails: half a nickel is okay but should be serviced, 9th nickel is to know orientation of which side is off. How do we test: rmi collimator test tool, all lines are radiopaque, collimate to edges of the box, once image is taken, the rulers are shown on image to read measurements, more accurate and precise vs nickel test. Center of x-ray field to center of ir alignment.
